The present invention relates to loudspeaker assemblies and particularly with loudspeaker assemblies which channel sound into relatively small enclosed areas.
The loudspeaker assemblies of the present invention are particularly suited to be mounted in the trunk area of an automobile and send the sound energy into the passenger compartment via a hole in the rear deck area of the automobile. It has been known to mount a loudspeaker on the trunk side of the rear deck of an automobile with the loudspeaker emitting sound into the passenger compartment. However, the sound emitted from this mounted loudspeaker have several disadvantages. First, there is a natural boominess to the loudspeaker. Boominess is a narrow frequency range of high resonance which causes sound in the narrow frequency range to become significantly augmented relative to the other parts of the frequency range of the loudspeaker. This boominess creates undesirable non-linearity of the sound reproduction. Second, the mounted loudspeaker, because it must be small to take up a minimum amount of room, cannot reproduce the low end of the audio spectrum with the efficiency that the middle and high ranges of the audio spectrum are reproduced. This inability to efficiently reproduce the low end of the audio spectrum also leads to non-linearity of the sound reproduction.
It has also been known to enclose a loudspeaker in a loudspeaker enclosure and mount this loudspeaker enclosure to the rear deck area, in a door panel or under the dash area of an automobile. These loudspeaker enclosures, however, must be small so as to take up a minimum amount of room in its mounted location. Thus, the loudspeaker enclosures suffer from the effects of incomplete damping of the backward wave from the loudspeaker, namely increased boominess from the compression on the loudspeaker cone. As well, these loudspeaker enclosures are also unable to efficiently reproduce the low end of the audio spectrum. This inability to efficiently reproduce the low end of the audio spectrum is caused by the fact that the loudspeaker enclosure cannot be of sufficient size to allow an increased efficiency by the recapturing of the backward going wave by the use of a tuned ports.
All of the prior loudspeaker installations in automobiles or other small enclosed spaces have used loudspeaker installations which take advantage of principles which are applicable to open air environments. It is possible, as will be described later, that the present invention has been successful in increasing the efficiency at the low end of the audio spectrum and has acted to dramatically decrease the natural boominess of the loudspeaker because, unlike the low impedance air of open air environments, the small enclosed air environments have high impedance air. If it is correct that the small enclosed air environments have high impedance air, the present invention, which acts to transform low impedance sound from the loudspeaker to high impedance sound, increases the efficiency of the reproduction of the low end of the audio spectrum because there is an impedance matching with the present invention which all previous loudspeaker designers and installers did not understand.
Even without considering the explanation of the possible reasons for the increased efficiency of the reproduction of the low end of the audio spectrum and the decreased boominess, the present loudspeaker assemblies have achieved never before achieved linearity of sound reproduction. As well, one of the present loudspeaker assemblies has achieved an outer configuration which allows it to be installed in most mass produced passenger cars without modification.